One setting, $padLocale, says which language and conventions a request is written in. The {trans} tag and the trans, currency and localDate functions all read it.

<?php

  // The page picks Dutch; an application listing $padLocales lets the visitor's
  // Accept-Language or ?lang= choose instead.

  $padLocale = 'nl';

  $count = 3;
  $user  = 'Ann';
  $total = 1234.5;
  $when  = '2026-10-05';

?>

<h4>{trans 'cart.title'}</h4>
<p>{trans 'cart.items', count=$count} - {trans 'cart.owner', name=$user}</p>
<p>{$total | currency('EUR', 'nl_NL')} - {$when | localDate('d MMMM y')}</p>

Catalogs

The texts live in _lang/<locale>.json, one flat object of keys:

{
  "cart.title": "Je winkelwagen",
  "cart.items": "%d artikel|%d artikelen",
  "cart.owner": "Bewaard voor :name"
}

• count= picks the plural form and replaces %d: two forms are one and other, three are zero, one and other.
• Every other name= replaces :name.
• A catalog is looked up like a _data file: from the page's directory up to the application root, then _common, the most specific winning. For nl_NL the files nl_NL.json, nl-NL.json and nl.json all count.
• A key no catalog knows is written as itself.

Choosing the locale

• $padLocale - the locale, 'en' unless the configuration or the page says otherwise.
• $padLocales - the locales the application speaks. When it lists any, a ?lang=nl link chooses one and the padLang cookie keeps it; without a choice the visitor's Accept-Language picks the best match.
• $padTimezone - the timezone dates are shown in.